Can you replace The rear wheel bearing or do have to the entire hub assembly on a 2003 ford expedition?

On a 2003 Ford Expedition, you generally cannot replace just the rear wheel bearing; it's integrated into the hub assembly. The hub assembly is a single unit that includes the bearing, and it's designed to be replaced as one piece. Trying to separate the bearing from the hub is usually not feasible and would likely damage the components. Therefore, you'll need to replace the entire rear hub assembly.